The invention is directed to a pump for supplying a fuel injection system and a hydraulic valve controller for internal combustion engines, having a first low-pressure side, having a first high-pressure side, and having means for feeding fuel from the low-pressure side to the high-pressure side.
Pumps of the type with which this invention is concerned are known in the most various embodiments as fuel injection pumps for internal combustion engines. On their low-pressure side, they communicate with a fuel supply tank, and with their high-pressure side, they feed for instance into the high-pressure fuel reservoir of a common rail fuel injection system or into the injection nozzles of the engine. Fuel injection systems in which a pressure step-up means is disposed between the injection pump and the injector or the injection nozzle are also known.
With ever more stringent demands made in terms of the exhaust gas limit values and fuel consumption of internal combustion engines, a promising approach to achieving these sometimes contrary demands is to control the valves hydraulically, preferably electrohydraulically.
The object of the invention is to furnish a pump which provides the supply both of fuel to a fuel injection pump and of a hydraulic fluid, hereinafter simply called fluid, to a hydraulic valve controller.
According to the invention, this object is attained by a pump for supplying a fuel injection system and for supplying a hydraulic valve controller for internal combustion engines, having a first low-pressure side, having a first high-pressure side, and having means for feeding fuel from the first low-pressure side to the first high-pressure side, in which a second low-pressure side, a second high-pressure side, and means for feeding a fluid from the second low-pressure side to the second high-pressure side are present.
This pump according to the invention has the advantage that a second pump for supplying fluid to a hydraulic valve controller can be omitted. This produces considerable cost savings, reduces the installation space required, simplifies sealing from the environment, and finally improves the efficiency of the engine, since only one pump has to be driven. Because of the presence of means for feeding fuel to a first high-pressure side and means for feeding a fluid to a second high-pressure side, it is equally possible to provide different pressure levels for supplying the fuel injection system and for supplying the hydraulic valve controller. By using a fluid adapted especially to the demands of the hydraulic valve controller, its operating performance can be improved further.
Variants of the invention provide that the means for feeding fuel from the first low-pressure side to the first high-pressure side and the means for feeding a fluid from the second low-pressure side to the second high-pressure side have at least one pump element, so that the advantages of the pump elements, known from the prior art, in fuel injection pumps can also be made use for the pump of the invention.
In a further feature of the invention, it is provided that the pump has a drive shaft that at least indirectly actuates the means for feeding fuel and the means for feeding a fluid, so that the coupling of the pump to the engine is effected in a simple, reliable way.
In another feature of the invention, the means for feeding fuel and/or the means for feeding a fluid are disposed radially to the longitudinal axis of the drive shaft, so that the advantages of the radial disposition, known from the prior art, of the means for feeding fuel also come into play in the pump according to the invention. Especially, when the drive shaft is an eccentric shaft, a deflection of the motion of the eccentric element or elements of the drive shaft can be omitted.
In a further variant of the invention, it is provided that the means for feeding fuel and the means for feeding a fluid each have at least two pump elements, disposed radially to the longitudinal axis of the drive shaft and opposite one another, so that the drive shaft is free of forces that engage crosswise to the longitudinal axis of the drive shaft. This avoids bending stress in the drive shaft and correspondingly reduces the bearing forces.
In a further feature of the invention, the pump element or pump elements disposed radially to the longitudinal axis of the drive shaft and opposite one another of the means for feeding fuel and the means for feeding a fluid are distributed uniformly over the circumference of the drive shaft, so that the torque to be transmitted from the engine to the pump drive shaft is made more uniform, and thus the torsional load on the drive shaft is also reduced.
In a further feature of the invention, the means for feeding fuel and the means for feeding a fluid are spaced apart from one another in the direction of the longitudinal axis of the drive shaft, so that a larger number of pump elements can be provided, which can be significant especially in engines with many cylinders. The spatial separation of the means for feeding fuel from the means for feeding a fluid also leads to simplifications in the hydraulic communication of the first and second low-pressure side with the first and second high-pressure side.
Further features of the invention provide that the pump is a radial piston pump or an in-line pump, so that the advantages, known from the prior art, of these types of pump also come into play in the pump of the invention.
In a further feature of the invention, it is provided that the quantity regulation of the means for feeding fuel and/or of the means for feeding a fluid is effected by means of an intake throttle on the first low-pressure side or the second low-pressure side, so that the pump of the invention also operates with good efficiency in the partial-load range.
In another variant of the invention, it is provided that the quantity regulation of the means for feeding fuel or of the means for feeding a fluid is effected by means of a recirculation valve on the first high-pressure side or the second high-pressure side, so that effective quantity regulation can be attained in a simple way.
In a further feature of the invention, the means for feeding a fluid feed fuel, so that the number of fuels is reduced, and furthermore internal leakage between the means for feeding fuel and the means for feeding a fluid cause insignificant impairment, if any, to the operation of the engine.
In a further feature, it is provided that the first low-pressure side and the second low-pressure side have the same fuel supply, so that only one low-pressure pump, connected upstream of the pump of the invention, is required, and the engineering expense is reduced.
In further features of the invention, the first high-pressure side communicates hydraulically with a high-pressure fuel reservoir or an injection nozzle and the second high-pressure side communicates hydraulically with a hydraulic valve controller, preferably an electrohydraulic valve controller, so that the pump of the invention can be integrated with an engine that has a fuel injection system and a hydraulic valve controller.